There are a couple of variables that will determine how far away your transmitter will work. There is only so much you can do with the transmitter in your car. Most garage door openers have a small wire about 6-8 inches long that picks up signals (older ones did anyways). I remember when I was a kid and into making all kinds of wierd gadgets (my dad is an electrician) I decided to see how far I could extend the range of our garage door opener. We had one of those old TV antennas on the roof of our house by the garage that hadn't been used for years. I took some small gauge wire and connected the antenna wire from the garage door opener to the outside TV anntena and that up the useable range for our openers from about 100 feet to three blocks. Not related to the transmitter, but as a point of safety, to prevent people from driving around with alot of transmitters to see who's garage they could break into, I switched the power outlet we plugged the garage door opener into so that we could shut the power off easily without having to unplug the unit. We would shut the it off every night once the cars were in, and if we were going to be away for a while.
1995 E420 - retired
1986 420SEL - retired